U.S. Pat. Nos. 6,788,455 and 6,967,774 have disclosed a microscope for wide angle observation for ophthalmic surgery which, by way of selectively addable optical units, allows an image of the fundus to be generated. The microscope includes a lens system, which includes a main objective and lenses disposed ahead of the main objective.
A disadvantage of this microscope is that the imaging quality in the wide angle observation is not ideal. As a result of the small distance between the main objective and the object to be observed, very short focal lengths result for a wide angle optical unit that can be added to the beam path. The wide angle optical unit can be adapted to the microscope by means of a further reduction optical unit which can be introduced into the beam path; however, this is linked to the disadvantage of a reduced imaging quality.
In addition to the optical disadvantages, the optical imaging systems in accordance with U.S. Pat. Nos. 6,788,455 and 6,967,774 have a relatively long installation length. In order not to unnecessarily hinder the user, for example a surgeon, in his work with the optical imaging system on the object, for example a patient eye, a reduction optical unit should only have a short installation length and additionally be disposed as closely as possible to the main objective.